Open reduction after exposure of all buttresses and internal fixation using 3-point mini-plate fixation provides the best stability [1]. Rinehart et al. reported that in cadaver studies, 2-point or 3-point mini-plate fixation is sufficient to withstand mastication, but 1-point mini-plate fixation is not sufficient to stabilize the zygomatic fracture against mastication [5]. Davidson et al. reported that 3-point fixation with mini-plates or interosseous wires allows little displacement, and 2-point fixation with mini-plates provides clinically acceptable stability [3]. Unlike these studies, Chen et al. reported that high surgical stability can be obtained even with a 1-point fixation using a single vestibular approach [6]. Kim et al. also reported that in the case of ZMC fractures without compound fractures, 1-point fixation on ZMB provides sufficient stability [7].
In the case of comminuted fractures not included in this study, it is necessary to perform as many fixations as possible without causing controversy. However, a consensus has not been established for the fixation method of two or three simple ZMC fractures.
Since the ZMC, like the mandible, is not a region that continues to function such as opening or mastication, considering the stability after surgery, we have doubts about whether all fractures should be fixed. In particular, if more than two points are fixed, the skin around the eyeball can be scarred when the FZ suture is fixed, and the mini-plates can be touched because of the thin skin. The ZMB can be fixed by intraoral approach, and it has an esthetic advantage if it can be fixed only in one site. In addition to the fixation method, since many other factors, such as the experience of the operator, the degree of postoperative edema affect the postoperative stability, if similar stability can be obtained, it has clinical value in that performing a smaller number of fixations can reduce the operation time and makes less postoperative complications.
In our study, it was confirmed that the number of fixation sites did not make a difference in the postoperative stability of fractures. As a similar study to our study, a domestic paper analyzed 29 patients in 2012 reported that 1-point fixation was clinically sufficient for ZMC fracture without comminuted fractures.
If you know the direction of the postoperative displacement, which can means a kind of “relapse” of the fractures, reduction of ZMC fracture can be done considering relapse after surgery. Through this, it produces a stable surgical outcome in the long-term period. For this reason, this study investigated the direction of postoperative fractured segment displacement.
It is said that the most influential factor as the cause of postoperative displacement of the fractured segment is masticatory force, and the masseter muscle has the greatest role among masticatory forces. In this study, the direction of the displacement of the unfixed end of the fractured segment was observed mainly in the inward direction. Dal Santo et al. postoperative fractured segments are said that the masseter muscle continues to function postoperatively, and the fractured segments continue to receive downward force, thereby causing the fractures to be displaced [8]. When viewed from the front, the masseter muscle originating from the zygoma and touching the mandibular angle travels slightly inwardly and diagonally, so when the masseter muscle functions, the force acts in the inward direction on the zygoma fractured segment, and this will determine the direction of postoperative position change of the fractured segment.
The limitation of this study is that the number of patients investigated was small, and the period of visit after surgery was short. In the future, more patients with ZMC fractures should be examined to confirm the results of this study. Also, in this study, the displacement direction was investigated only in the coronal plane, but the displacement direction in the axial and sagittal planes should also be investigated. In addition to this, a comparative study on the postoperative stability of the cases of using an absorbent plate and non-absorbable plates is also considered meaningful.